The invention described is primarily for a cochlear prosthesis, or implantable hearing prosthesis system, or bionic ear. That is, a system of components designed with the object of restoring some sensations of hearing to the profoundly deaf. The main object of the invention is to improve speech communication, but the importance of awareness of environmental sounds is also taken into account.
In many people who are profoundly deaf, the reason for deafness is absence of, or destruction of the hair cells in the cochlea which transduce acoustic signals into nerve impulses. These people are thus unable to derive any benefit from conventional hearing air systems, no matter how loud the acoustic stimulus is made, because there is no way nerve impulses can be generated from sound in the normal manner.
The cochlear implant system seeks to bypass these hair cells in the cochlea by presenting electrical stimulation to the auditory nerve fibers directly, leading to the perception of sound in the brain. There have been many ways described in the past for achieving this object, including implantation of electrodes in the cochlea connected to the outside world via a cable and connector attached to the patient's skull; to sophisticated multichannel devices communicating with an external computer via radio frequency power and data links.
The invention described herein comprises a multichannel electrode implanted into the cochlea, connected to a multichannel implanted stimulator unit, which receives power and data from an externally powered wearable speech processor, wherein the speech processing strategy is based on known psychophysical phenomena, and is customized to each individual patient, by use of a diagnostic and programming unit.
In order to best understand the invention, it is necessary to be aware of some of the physiology and anatomy of human hearing, and have a knowledge of the characteristics of the speech signal. In addition, since the hearing sensations elicited by electrical stimulation are different from those produced by acoustic stimulation in a normal hearing person, it is necessary to discuss the psychophysics of electrical stimulation of the auditory system.